Outcome Measures Associated with Perceived Stress

Fig. 9.1

Correspondence between patient-reported symptoms of tinnitus and the diagnostic symptoms of anxiety and depression. Symptoms of tinnitus are based on a qualitative analysis of patient-reported complaints collated by Watts et al. (2016) and Tyler and Baker (1983). Mental health symptoms are based on DSM-5 criteria for generalised anxiety and persistent and major depression (American Psychiatric Association 2013). Functional impacts that impair quality of life are not included here, but are common to all conditions. These impacts include but are not restricted to avoidance behaviours, reduced social participation and negative effect on work

9.4 Measuring Perceived Stress Associated with Tinnitus

The Tinnitus Reaction Questionnaire (TRQ) was constructed in Australia in 1991. It was designed specifically to measure a single attribute of tinnitus: the perceived stress related to tinnitus (Wilson et al. 1991). The TRQ selectively measures perceived stress associated with tinnitus. It has 26 items which all start off with the phrase ‘My tinnitus has…’ (see Fig. 9.2 for examples). Ratings for each item are made on a 5-point Likert scale (scored 0–4) with the category labels (not at all/a little of the time/a good deal of the time/almost all of the time). Scoring involves the simple addition of the category score selected by the respondent. This gives a range of scores from 0 to 104, with a high score representing greater distress. There is very little literature on the psychometric properties of the TRQ. Although Wilson et al. (1991) describe four factors resulting from their factor analysis (general distress, interference, severe distress, avoidance behaviours), the statistical outputs from the factor analysis show that most of these items are very closely related to one another. So there is little value in treating this questionnaire as if it has multiple subscales. A single global score is adequate.

Fig. 9.2

Items taken from the Tinnitus Reaction Questionnaire (Wilson et al. 1991) and mapped onto the symptoms of tinnitus and the symptoms of anxiety and depression. Symptoms of tinnitus are based on Watts et al. (2016) and Tyler and Baker (1983). Mental health symptoms are based on DSM-5 criteria for generalised anxiety and persistent and major depression (American Psychiatric Association 2013). Functional impacts are not included here, but are common to all conditions. These impacts include but are not restricted to avoidance behaviours, reduced social participation, negative effect on work and impaired quality of life

If a questionnaire looks like it is going to measure what it is supposed to measure, then it has what is termed ‘face validity’. To assess the face validity of the TRQ, Fig. 9.2 illustrates how the 26 items map onto the framework of stress-related complaints already presented in Fig. 9.1. The wording of each item was carefully evaluated for its meaning, and it was ascertained whether it would fit within one of the symptom domains. Only 3 of the 26 items appear to be restricted to tinnitus-related stress (#04 My tinnitus has made me feel angry, #09 My tinnitus has made me feel annoyed, #17 My tinnitus has made me feel frustrated with things). Section 8.​5 considers how many of the remaining tinnitus-related complaints share characteristics with impaired psychological well-being.

The impetus for the construction of the TRQ came from a need for a reliable measurement instrument for evaluating the effects of psychological interventions on the ability of people to cope with tinnitus (Ireland et al. 1985). Up until this point, tinnitus-related questionnaires were purposefully broad in scope, and they included items that asked patients about a wide variety of complaints. The Tinnitus Questionnaire (Hallam et al. 1988) and the Tinnitus Handicap Questionnaire (Kuk et al. 1990) are both good examples of broad-ranging multi-attribute questionnaire instruments that were constructed before the TRQ, but they measure much more than simply perceived stress.

The Tinnitus Questionnaire has 52 items. Ratings for each item are made on a 3-point Likert scale (scored 0–2) with the category labels (true/partly true/not true). Only 41 items are scored, and the total score is scaled so that the global score ranges from 0 to 82, with higher score indicating greater severity of tinnitus symptoms. The first assessment of the psychometric (statistical) properties of the Tinnitus Questionnaire, using factor analysis techniques, identified three orthogonal factors covering (1) emotional distress, (2) auditory difficulties and (3) sleep disturbance (Hallam et al. 1988). A later reinvestigation by Hallam in 1996 using data from a different sample of tinnitus patients identified five orthogonal factors covering (1) emotional and cognitive distress, (2) intrusiveness, (3) auditory perceptual difficulties, (4) sleep disturbance, and (5) somatic complaints. Hence, there is some uncertainty about what domains of tinnitus-related complaints are measured by the Tinnitus Questionnaire.

The Tinnitus Handicap Questionnaire has 27 items. Ratings for each item are made on a 100-point numerical scale (from 0 = strongly disagree to 100 = strongly agree). The total score is scaled so that the global score ranges from 0 to 100, with higher score indicating greater severity of tinnitus symptoms. The Tinnitus Handicap Questionnaire has three subscales covering (1) social, emotional and physical effects of tinnitus, (2) hearing ability and unease and (3) the individual’s perception of tinnitus. It has been pointed out that items on the first two subscales are very closely related to one another, both in terms of the semantic content (i.e. meaning) of the items and the statistical outputs from the factor analysis (see Kennedy et al. 2004; Fackrell et al. 2014). These observations indicate that the Tinnitus Handicap Questionnaire is particularly sensitive to the social, emotional and physical functioning aspects of tinnitus-related distress, but arguably this subscale actually covers three different discrete domains.

Although this summary of tinnitus-related questionnaires is not exhaustive, it serves to highlight the general emphasis on questionnaires that measure a broad range of dimensions of tinnitus complaint. Later questionnaires are little different in this respect (e.g. Tinnitus Handicap Inventory, Newman et al. 1996). Unlike these broad-scope questionnaires, the developers of the TRQ were explicit in their aim to assess a narrow range of tinnitus characteristics. In other words, their aim was to create a single-attribute questionnaire instrument that focused on perceived stress associated with tinnitus.

Given the overlap in patient-reported complaints for tinnitus, anxiety and depressive symptoms, one should expect a high degree of association between tinnitus-related questionnaire scores and questionnaire scores for anxiety and/or depression. Convergent validity is a term that describes the extent to which the underlying construct of one questionnaire corresponds to other questionnaire constructs that are theoretically similar. It is measured by calculating the correlation coefficients between the questionnaire scores and assessing the strength of the association. Convergent validity is indicated by a strong Pearson correlation coefficient (r > 0.60) (Andresen 2000). The TRQ has been examined by correlating with scores for depression and anxiety questionnaires. TRQ has strong convergent validity with the Beck Depression Inventory (BDI) (Beck et al. 1961). Wilson et al. (1991) reported correlations of r = 0.63 and r = 0.87 for two independent samples of participants, while Robinson et al. (2003) reported a correlation of 0.66. With respect to anxiety, TRQ also correlates well. Correlation coefficients reported by Wilson et al. (1991) were 0.60 and 0.74 for state anxiety and 0.58 and 0.71 for trait anxiety, as measured by the State-Trait Anxiety Inventory (STAI) (Spielberger et al. 1970). Overall, the TRQ seems to be measuring similar theoretical constructs associated with general perceived stress. These findings raise an important question about whether the TRQ measures any sufficiently distinct aspect of tinnitus-related stress that is not captured by measures of general psychological well-being.

9.5 Associations Between Tinnitus and Psychological Well-Being

From the patient-reported complaints (Sect. 9.3), it is clear that tinnitus is associated with considerable perceived stress manifest as feelings of anxiety, sadness or depression, irritability, inability to relax, etc. These symptoms are not restricted to tinnitus. Symptom overlap in tinnitus, depression and anxiety can act as a confounder in estimating the severity of either condition. Figure 9.1 illustrates this point by mapping out the correspondence between patient-reported symptoms of tinnitus and the diagnostic symptoms of generalised anxiety and depression according to the Diagnostic and Statistical Manual for Mental Disorders (DSM) edition 5 (American Psychiatric Association 2013). Four of the patient-reported complaints reported by people with tinnitus seem common to all three conditions (poor concentration, sense of loss of control, sleep disturbance and irritability). Three further complaints are common to tinnitus and anxiety (fear, feelings of anxiety or stress and inability to relax), and three more are common to tinnitus and depression (feelings of sadness or depression, feeling imperfect and feelings of hopelessness). This high degree of association is also seen in the construction of the TRQ. Turning to Fig. 9.2, one can see how 18 of the 26 items from the TRQ appear to map onto domains relating to general anxiety or depression (or the intersections thereof). Associations between tinnitus and psychological well-being have important implications when we turn to discuss how perceived stress is measured.

9.6 Measuring General Perceived Stress

One of the most widely used measures of stress is the Perceived Stress Scale (PSS), developed in the USA (Cohen et al. 1983). This questionnaire was designed specifically to measure global perceived stress. Up until this point, measurements of stress typically focused on objective indicators (e.g. frequencies) of specific stressors such as chronic illness, bereavement, and retirement. But this focus on external life event stressors and the cumulative minor stressors of everyday life overlooked the influence on individual’s subjective interpretation of that stressor.

The PSS therefore asks questions about whether a person feels under pressure from specific worries. It has 14 items which ask individuals to rate how often they experienced particular feelings and thoughts in the past month. Items were designed to tap into how unpredictable, uncontrollable and overloaded people find their lives. An example item is ‘In the last month, how often have you felt that you were unable to control the important things in your life?’ Ratings on each item are made on a 5-point Likert scale (scored 0–4) with the category labels/never/almost never/sometimes/fairly often/very often. Seven of the items are positively worded and seven are negatively worded. The positive items are reverse scored, and then the global score is the sum across all 14 items. A high score therefore reflects a high degree of perceived stress with the global score ranging from 0 to 56.

The first major assessment of the psychometric properties of the PSS, using factor analysis techniques, identified two orthogonal factors covering (1) the negatively worded items (e.g. been upset, unable to control things, felt nervous and stressed) and (2) the positively worded items (e.g. dealt successfully with hassles, effectively coping, felt confident) (Cohen and Williamson 1988). Informed by this dataset, a shorter 10-item version was produced, and again this had the same two-factor structure.

Results for convergent validity have been usefully summarised as part of a systematic review of the psychometric properties of the PSS (Lee 2012). Overall findings support the conclusion that the questionnaire score is either moderately or strongly correlated with scores for depression and anxiety questionnaires, as measured using the BDI, Hospital Anxiety and Depression Scale (HADS) (Zigmond and Snaith 1983), STAI, and Depression, Anxiety and Stress Scale (DASS) (Lovibond and Lovibond 1995). These findings indicate that the PSS seems to be measuring similar theoretical constructs associated with stress.

The Perceived Stress Questionnaire (PSQ) is also concerned with the cognitive appraisal about aspects of everyday life and the emotional reaction to them (Levenstein et al. 1993). Many of the questions have the format ‘you feel…’. For example, ‘You feel that too many demands are being made on you/You feel frustrated’. The original PSQ comprised 30 items, spanning seven factors (harassment, irritability, lack of joy, fatigue, worries, tension and overload). Ratings for each item are made on a 4-point Likert scale (scored 1–4) with the category labels/almost never/sometimes/often/usually. Raw scores are transformed into a stress index from 0 (lowest possible level of stress) to 1 (highest possible level of stress). Just as in the PSS, one version of the PSQ asks individuals to rate how often they experienced particular feelings and thoughts in the past month. A second version of the PSQ asks about events in the past 2 years.

The ‘past month’ version of the PSQ demonstrated acceptable convergent validity with the PSS (r = 0.73) and trait anxiety measured using the STAI (r = 0.75), but weaker correlations with depression (r = 0.56).

In 2001, the PSQ was translated into German and re-evaluated on a broad sample of participants (Fliege et al. 2001). The resulting German version has a reduced set of 20 items, covering four factors (joy, worries, tension and demands). Although the labels given to three of the factors are equivalent across languages, it is important to note that the items that correspond to the factors are different. Thus, any subscale scores should not be directly compared across the English and German versions.

The DASS (Lovibond and Lovibond 1995) is another widely used questionnaire that includes a measure of perceived stress. This questionnaire comprises 42 items covering three separate scales of stress, anxiety and depression over the past week. Each scale has 14 items. For example, one of the stress scale items is ‘I found myself getting upset by quite trivial things’. Ratings for each item are made on a 4-point (scored 0–3) with the following category labels: did not apply to me at all/applied to me to some degree, or some of the time/applied to me to a considerable degree, or a good part of time/applied to me very much, or most of the time. Scores of depression, anxiety and stress are calculated by summing the scores for the relevant items and are interpreted according to five symptom severities (normal, mild, moderate, severe and extremely severe).

There is relatively little data on the DASS in tinnitus. However, one article does report questionnaire findings in a sample of 100 patients with tinnitus attending an out-patient otorhinolaryngology clinic (Gomaa et al. 2014). Severe to extremely severe stress was observed in 33% of patients. The proportion of patients with severe to extremely severe depression and anxiety was somewhat greater (51% and 54%, respectively). Figure 9.3 shows the pattern of stress, anxiety and depressive comorbidities in this sample, plotted as a function of tinnitus ‘severity’. Tinnitus severity was measured using a Visual Analogue Scale.

9.7 Applications of Stress-Related Questionnaire Instruments

The discussion so far has shown how patient-reported complaints have informed the construction of questionnaire instruments and has demonstrated the commonalities between complaints of tinnitus, stress, anxiety and depression. None of the issues so far concerning questionnaire construction are necessarily restricted to outcomes used to evaluate treatment-related change. They are equally applicable to the purposes of screening, diagnosis and prognosis. However, the way that a questionnaire is constructed should be informed by the purpose for which it is intended. Tutorial 9.2 explains more about these different applications. This section considers how the intended application of each stress-related questionnaire defines what statistical properties of the instrument are most important during its creation.

Tutorial 9.2 Purpose of Questionnaires

Potential applications of such questionnaires typically fall into three broad categories (Kirschner and Guyatt 1985):

Discrimination. A discriminative tool is used to distinguish between individuals or groups, generally as part of a screening or diagnostic procedure. For example, to quantify the burden of stress on individual tinnitus patients so that healthcare provision can be tailored more effectively.

Prediction. A predictive tool is used to classify individuals into predefined categories generally as part of a screening or diagnostic procedure. For example, to identify clues to a prognosis.

Evaluation. An evaluative tool is used to measure the magnitude of change over time in an individual or group on the complaint of interest. For example, to quantify treatment benefits in clinical trials and for measuring quality-adjusted life years in cost-utility analysis.

It is not unusual for developers of tinnitus-related questionnaires to claim that theirs is a multipurpose instrument. For example, on the TRQ, Wilson et al. (1991) claimed ‘such a scale may provide a useful assessment device in clinical practice and in further research on psychological aspects of tinnitus. It may be useful as a screening instrument in the selection of distressed samples, as a means to distinguish tinnitus sufferers who cope with the problem from those who do not cope well, and as a measure of psychological distress before and after treatment’ p. 198.

For questionnaires assessing how a person feels and functions in day-to-day activities, the psychometric (statistical) requirements to maximise the discriminative, predictive or evaluative properties of the questionnaire are often at odds with one another. Table 9.1 describes key issues to be considered when devising a strategy for constructing a questionnaire for discrimination or for evaluation. Prediction is not discussed further because it is not an issue that has been widely investigated in the tinnitus field.

Table 9.1

Major issues for consideration in the construction and evaluation of outcome instruments (informed by Kirschner and Guyatt 1985)

Issue to consider

Discriminative strategy

Evaluative strategy

Selecting the questionnaire items

Complaints are:

• Important to patients with tinnitus

• Universally applicable to people with tinnitus

• Stable over time

Complaints:

• Are likely to change

• Will be responsive to a clinically significant change,

as a result of the intervention of interest

Choosing the format of the response options available to patients

• Short response sets which facilitate the same interpretation from person to person

• Response sets have sufficient gradations to register change

Reducing the total item pool based on performance in the relevant setting

• Remove items where variability between-subjects is not related to tinnitus

• Consider time and effort needed by the subject

• Remove unresponsive items

Ensuring measurement of true differences relative to the overall variance

• Variation between subjects is large and remains stable across testing intervals

• Include all characteristics of tinnitus that are common to most people

• Relationship between the instrument score and external measures at a single point in time

• Include only characteristics that are salient with respect to clinically important treatment-related change.

• Relationship between changes in the instrument score and external measures over time

Responsiveness

• N/A

• Known power of the test to detect a minimal clinically important difference (i.e. all parameters for computing the sample size required to observe a predefined change in the population)

For those readers particularly interested in the measurement properties of patient-reported outcome instruments, the COSMIN checklist (​www.​cosmin.​nl/) is a useful generic tool for evaluating the methodological quality of studies reporting the construction of an instrument.

While a discriminative strategy places an emphasis on attempting to sample all important, relatively stable aspects of functional status common to most members of each functional class, an evaluative strategy places an emphasis on restricting measurement only to those salient activities and feelings that are subject to clinically important treatment-related change. Kirschner and Guyatt (1985) point out that this distinction has often been neglected in the health status measurement literature. An outcome instrument for measuring stress-related symptoms in people with tinnitus before and after (psychological) treatment should certainly not be seeking to assess all of the 20 distinct domains of tinnitus-associated complaints that are given in Fig. 9.1. Criticism of tinnitus questionnaires that ‘measure a limited number of constructs’ (p. 144) (Newman et al. 1996) is not a valid criticism for questionnaires that are primarily to be used for an evaluative (outcome) purpose.

Suffice it to say that few tinnitus-related questionnaires have been developed specifically according to an evaluative strategy (Fackrell et al. 2014). And the TRQ, PSS, PSQ and DASS are no exceptions. Their psychometric properties as outcome instruments in the tinnitus population are not yet established.

9.7.1 Use of Questionnaires for Diagnosing Perceived Stress

Just like other chronic conditions, tinnitus in the general population is associated with perceived stress and its associated symptoms of anxiety and depression. Table 9.2 lists some of the instruments that have been used for assessing stress, anxiety and depression in tinnitus research. Consistent with the previous descriptions, these are classified according to measures of perceived stress associated with tinnitus, general perceived stress, anxiety and depression.

Table 9.2

List of instruments used for assessing stress, anxiety and depression in clinical research